ThompsonConstructor.cpp

#include "ThompsonConstructor.h"
using namespace std;

NFA *ThompsonConstructor::constructChar(char c)
{
    NFA *nfa = new NFA("constructed nfa");
    State *startState = new State(false);
    State *finishState = new State(true);
    nfa->addState(startState);
    nfa->addState(finishState);

    nfa->setStartState(startState);
    startState->addTransition(c, finishState);

    return nfa;
}

NFA *ThompsonConstructor::construct(RegexNode *ast)
{
    NFA *L;
    NFA *R;
    if (!ast)
        return nullptr;
    switch (ast->type)
    {
    case 'c':
        return constructChar(ast->value);
        break;
    case '*':
        L = construct(ast->left);
        return NFA::kleeneStar(L);
        break;
    case '|':
        L = construct(ast->left);
        R = construct(ast->right);
        return NFA::alternation(L, R);
        break;
    case '.':
        L = construct(ast->left);
        R = construct(ast->right);
        return NFA::concatenation(L, R);
        break;
    default:
        return nullptr;
        break;
    }
}